This research identifies the necessary foundations to point out the proper method of interpreting the norms of Regulatory Law. To reach this point, however, this thesis goes through the discussion of which is the proper method of interpreting the Constitution and the statutes in general. The (practical) results of the constitutional theories or of the theories of legal interpretation depend on factors that are often overlooked, which affects obviously in the correctness of these theories, resuming the discussion of legal formalism, with more robust arguments in its favor. The proposed hypothesis is that the Brazilian theorists of constitutional and legal interpretation generally develop their theories as if they would be applied by themselves or by prominent experts and / or with abstract criteria, neglecting the fact that the proposed interpretive rule may result in an inappropriate Law, at the operational level, given the limitations of the agents responsible for its implementation and real-world contingencies. In Regulatory Law, specifically, a better law is obtained if a deferential formalism (or maximilianist formalism) is adopted by the judges as interpretive standard, rather than a non-formalist interpretive standard, such as the post-positivist and the neoconstitucionalist one. There are external factors that affect decisively the ability to enforce the Constitution and the statutes, which are not perceptible to the moral and / or conceptual-theoretical analysis. So, if not identified and adequately addressed, these factors lead to the elaboration of a constitutional or legal interpretation theory that lacks substantial practical value, and which enforcement will generate dysfunctions in the constitutional and legal system, and also a bad law. It is proposed that the appropriate law and legal interpretation is identified from a perspective other than the moral or theoretical-conceptual-abstract perspective, to show that there are solid theories opposing a moral reading of the Constitution by the judiciary branch, and that the defense of the practical application the moral reading of the Constitution depends on previous analyzes generally neglected by their defenders. This moral reading can yield unexpected (negative) results. This other perspective, especially important for the choice of interpretive method, would be institutional. To call the scholars and public servants in general to use perfectionism in the application of law may lead, and often leads to a bad law. It may even negatively impact the functioning of the republican system (the role and responsibility of institutions) and democracy (legitimacy of the deciding institutions) of the State. The conclusion of this research is that the majority of the legal and constitutional issues are decided by the Legislature and the Public Administration. They do not even reach the courts. It was noted that of the Legislature and the Public Administration have greater decision-making capacity, when compared to the courts, in regard to the choice of interpretive rules and theories, as well as in the interpretation of vague, ambiguous and principle-oriented legal provisions, especially in matters of extreme complexity and technicality, such as the regulatory standards and related constitutional provisions. On the other hand, we identified a greater decisionmaking ability of the courts within legal provisions that are clear and specific (legal rules). It was noticed that the Federal Supreme Court (STF) and the Superior Court of Justice (STJ) generally share this view, adopting a deferential formalist approach regarding regulatory standards, even though the majority of Brazilian legal scholars tend to follow the opposite direction. Thus, observing the shift of the paradox of omnipotence towards the Judiciary, intensified in Brazil after the 1990s, we believe that the adoption of deferential formalism interpretive standard by the judges is strategic. On the other hand the Public Administration and the Legislature should adopt a non-formalistic interpretation approach. Since the formalist approach recommends deference to interpretations of institutions with greater decision-making capacity, the result of the application of the law in general would be close to that required for non-formalist theories, with their clarification and specification.